Can purchase the Cauldron from the girl named Sillia Herald in Bloody Kith. She's right next to zone in. (North of zone-in) Near assistant Joseph. Have to look around, she's hiding near some trees.
Be advised, either have all of your subcombines on your person (all 22 of them) or use the campfire and bind at Tavid in the guild lobby to complete this item. Each subcombine eats the cauldron, so you'll need one for the red bloods, one for the orange bloods, one for the blue bloods, and a final one for the last 3 items.
I didn't have that much bag space, so that's what I had to do. It's terribly inconvenient, but the aug's well worth it.
Would it have killed SOE to make the cauldron not get eaten on the subcombines?!?!